docs: def pkcs_emsa_pss_encode(M, emBits, h, mgf, sLen): 
      """
      Implements EMSA-PSS-ENCODE() function described in Sect. 9.1.1 of RFC 3447
  
      Input:
         M     : message to be encoded, an octet string
         emBits: maximal bit length of the integer resulting of pkcs_os2ip(EM),
                 where EM is the encoded message, output of the function.
         h     : hash function name (in 'md2', 'md4', 'md5', 'sha1', 'tls',
                 'sha256', 'sha384'). hLen denotes the length in octets of
                 the hash function output. 
         mgf   : the mask generation function f : seed, maskLen -> mask
         sLen  : intended length in octets of the salt
  
      Output:
         encoded message, an octet string of length emLen = ceil(emBits/8)
  
      On error, None is returned.
      """
  
      # 1) is not done
      hLen = _hashFuncParams[h][0]                             # 2)
      hFunc = _hashFuncParams[h][1]
      mHash = hFunc(M)
      emLen = int(math.ceil(emBits/8.))
      if emLen < hLen + sLen + 2:                              # 3)
          warning("encoding error (emLen < hLen + sLen + 2)")
          return None
      salt = randstring(sLen)                                  # 4)
      MPrime = '\x00'*8 + mHash + salt                         # 5)
      H = hFunc(MPrime)                                        # 6)
      PS = '\x00'*(emLen - sLen - hLen - 2)                    # 7)
      DB = PS + '\x01' + salt                                  # 8)
      dbMask = mgf(H, emLen - hLen - 1)                        # 9)
      maskedDB = strxor(DB, dbMask)                            # 10)
      l = (8*emLen - emBits)/8                                 # 11)
      rem = 8*emLen - emBits - 8*l # additionnal bits
      andMask = l*'\x00'
      if rem:
          j = chr(reduce(lambda x,y: x+y, map(lambda x: 1<<x, range(8-rem))))
          andMask += j
          l += 1
      maskedDB = strand(maskedDB[:l], andMask) + maskedDB[l:]
      EM = maskedDB + H + '\xbc'                               # 12)
      return EM